public void ProcessRequest (HttpContext context) {

        FtpWebRequest request = (FtpWebRequest)WebRequest.Create("serverpath" + "filename");
        request.UsePassive = false;
        request.Credentials = new NetworkCredential("user", "pass");

      //  byte[] fileBytes = null;

        using (FtpWebResponse response = (FtpWebResponse)request.GetResponse())
        {
            using (Stream responseStream = response.GetResponseStream())
            {
                context.Response.Cache.SetCacheability(HttpCacheability.NoCache);
                context.Response.ContentType = MediaTypeNames.Application.Pdf;
                context.Response.AddHeader("content-disposition", "attachment; filename=test.pdf");
                context.Response.BufferOutput = false;   // to prevent buffering 
                //context.Response.Buffer = true;
                context.Response.Clear();

                byte[] buffer = new byte[262144];
                int bytesRead = 0;
                while ((bytesRead = responseStream.Read(buffer, 0, buffer.Length)) > 0)
                {
                    context.Response.OutputStream.Write(buffer, 0, bytesRead);
                }
                context.Response.OutputStream.Flush();
                context.Response.OutputStream.Close();
                context.Response.End();
            }
        }

        request.Abort();
        context.ApplicationInstance.CompleteRequest(); 
    }